TIEG and estrogen modulate SOST expression in the murine skeleton.

Area of Science:

• Bone Biology
• Endocrinology
• Molecular Genetics

Background:

• TIEG knockout mice show reduced bone density, linked to human osteoporosis.
• Sclerostin (SOST) is upregulated in TIEG-deficient mice, suggesting TIEG regulates SOST.
• TIEG is an estrogen-regulated gene, and hormonal changes affect SOST expression.

Purpose of the Study:

• Investigate the role of TIEG in regulating SOST expression.
• Determine the influence of estrogen and microRNAs on SOST in different bone compartments.

Main Methods:

• Utilized TIEG knockout mice and osteocyte cell lines (IDG-SW3).
• Employed promoter deletion, chromatin immunoprecipitation, shRNA, and CRISPR-Cas9 for gene regulation studies.
• Conducted ovariectomy (OVX) and estrogen replacement therapy (ERT) in mice, followed by miRNA and mRNA sequencing.

Main Results:

• TIEG suppresses SOST promoter activity; TIEG knockdown increases SOST and delays mineralization.
• SOST expression differs between cortical (higher) and trabecular bone.
• OVX and ERT differentially affect SOST expression in cortical and trabecular bone, with estrogen and miRNAs playing key roles.

Conclusions:

• TIEG is a critical regulator of SOST expression in bone.
• Estrogen and specific miRNAs are involved in modulating SOST levels in response to hormonal changes.
• These findings highlight TIEG and estrogen-regulated miRNAs as potential therapeutic targets for osteoporosis.